Fuel economy seems to be the biggest rave lately. We have
seen crazy ideas in the past few years, everything from low rolling resistance
tires to a hybrid Porsche! (Porsche 918 Spyder for those curious individuals
out there) There's even been studies conducted that shows you would save more
gas using the A/C instead of opening the windows once you exceed 80 km/h (about
50 MPH) due to wind resistance.
Going back to low rolling resistance tires though, are they
really worth the extra dollars? If you look at my chart below, the Michelin
Energy Saver All-seasons cost a whopping $230 more than the regular
OEM-equivalent replacement all-season tires - Bridgestone Insignia SE200's. For the
purposes of comparison in this article, we will be looking at the prices from
Canadian Costco only. The MPG figures are based on a 2009 Toyota Prius, fuel
economy data were grabbed from a report on Tirerack.com (a reputable online
retailer of tires and car parts/products based in the USA, link below). I have
made my best guess for the missing numbers based on the Tire Rack numbers,
these estimated figures are denoted with a "?" after the number.
The short answer is, yes the low rolling resistance tires do
offer you enough of a benefit to offset the extra costs in purchasing the
tires. Performance of these low resistance tires is also not a problem because the
difference won't be noticeable if your driving is not too "spirited".
It's been said that the earlier generations of low resistance tires encountered
poor wet surface performance, based on the reviews and articles on Tire Rack it
seems to have been fixed in later editions of low resistance tires.
Here's the chart from my calculations based on the prices
($CDN) from Costco and the test data from Tire Rack:
Please be aware that the last two rows are regular
all-season tires, the first three rows are the low rolling resistance tires. The
Bridgestone Ecopia EP100 is a summer low resistance tire, and the EP422 is the
all-season version. The Bridgestone Insignia SE200 is the tire I used for base
comparison, since it is a regular all-season tire just like the Goodyear
Integrity I have assumed the MPG figures for those two will be the same if not
very similar. I had to use the Insignia tires for my calculations because
unfortunately Costco in Canada doesn't carry the Goodyear's. Ideally I would've
used the Goodyear for my calculations because that's the tire used in the Tire
Rack tests.
Focusing on the last two columns in my chart – highlighted
in green, you will see that the fuel savings over five years far exceeds the
extra costs for the tires. The time frame of five years was chosen because
either one of two things will happen: 1) the treads are worn, or 2) the rubber is
near the end of its useful life and large cracks are presents.
Wait! These fuel consumption numbers are from a Prius, will
it apply to other cars?
You can use the same calculations but make sure you keep the
ratios the same. So in here we see that the Michelin's fuel consumption is 0.892
times of the regular Bridgestone Insignia all-seasons, use that same factor for
your car's current fuel economy data (e.g. 7.5 L/100KM) and recalculate the
litres per year and dollar amounts. The conclusion should be the same and
actually, the less fuel efficient your car is compared to a Prius, the bigger
the net savings you should realize because the price of the low resistance
tires are fixed but the fuel savings will grow with fuel consumption. Don't believe me? See the chart
below. The fuel consumption numbers highlighted in yellow are the extrapolated numbers. Now the ratio method of extrapolating data isn't as accurate as real test
data done with your car but you likely won't find data specific to your car
online, this is the most logical method given the constraints of information.
Well there you have it folks, get low rolling resistance
tires the next time you replace your tires!
Tire Rack test figures: http://www.tirerack.com/tires/tests/testDisplay.jsp?ttid=121
Have a wonderful weekend everyone, sorry I haven't been able
to update this blog as frequently...things have been quite busy lately.
-TT
